Polyimides are known to be useful high performance polymers. Polyetherimide sulfones are a particular class of polyimides which combine the high temperature characteristics of polyimides but still have sufficient melt processability to be formed by conventional molding techniques such as compression molding, gas assist molding, profile extrusion, film extrusion, thermoforming and injection molding. Good melt processability is a key attribute for polyetherimides. It allows them to be quickly and easily formed into articles by extrusion and molding processes. Polyetherimide sulfones with higher heat capability, as reflected in higher glass transition temperature (Tg), are desirable to replace traditional materials of construction such as metal, glass and ceramic. However as higher Tgs are obtained the temperatures needed to melt these polymers and form them into items increases. At these extremely high melt processing temperatures even the most stable polymer linkages can decompose. In polyetherimide sulfones such instability is often indicated by a rise in melt viscosity or an increase in the energy needed to stir or push the molten polymer. This is especially problematic, as the increasing viscosity requires more mechanical work to move the melt generating more heat through friction, giving even higher temperatures that cause further resin degradation. In some cases this resin melt instability results in so much degradation that the polyetherimide sulfone is no longer a thermoplastic; it is crosslinked into infusible crumbs and cannot be formed into articles. Thus there is an ongoing need to improve the melt stability of high Tg (>250° C.) polyetherimide sulfones.